How do you deal with friends who keep asking for favors?

I notice that friends ask me some advice in careers and money management. I think it is nice that I can be of help to them, but I am becoming resentful.

Why I am resentful? Because I worked hard to gain that knowledge and spent time researching it. I had couple of failures and mistakes were made. When I was in trouble, there wasn't a friend who offered me the answer.

I only had my family and this TRP knowledge to get through.

When I help them, they do thank me. However, I don't think their thankfulness is sincere either. When I ask for a difficult favor in return, they come up with lame excuses. I am being a bit arrogant here, but I sometimes feel these friends are just there because they want to learn some stuff from me.

How do you deal with them? Cut them off cold?

In retrospect, how do I befriend with better guys then me? I sometimes think why would better guys hangout with me, if I can't offer them a value they don't have?